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9 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is the best-known trade name for diphenhydramine?
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Benadryl
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Outside the United states and Canada Benadryl products may contain a different antihistamine (e.g. UK) or no antihistamine at all (e.g. Australia).
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What is the functional class of diphenhydramine?
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Antihistamine
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Diphenhydramine also has anticholinergic, antitussive, antiemetic and sedative properties.
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What is the mechanism of action of diphenhydramine?
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Blocks histamine H1 (bronchoconstriction, peripheral vasodilation) receptors, and blocks acetylcholine receptor sites (anticholinergic). Also useful in reversing dystonic reactions caused by certain antipsychotic medications that block histamine receptor sites (Thorazine, Compazine, Reglan, Haldol, Phenergan).
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Diphenhydramine is actually an inverse agonist of the histamine H1 receptor
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What are the listed indications for diphenhydramine?
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- Anaphylaxis
- Moderate to severe allergic reactions - Acute extrapyramidal (dystonic) reactions |
Diphenhydramine is also used to treat motion sickness and insomnia
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What are the listed contraindications for diphenhydramine?
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- Hypersensitivity
- Newborns and nursing mothers |
Some sources state that diphenhydramine is condraindicated in patients <2 years old
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What are the listed precautions for diphenhydramine?
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- Not considered a primary drug for the treatment of severe allergic reactions or anaphylaxis
- Use with caution if the patient has narrow-angle glaucoma |
Diphenhydramine appears on the Beers Criteria for Potentially Inappropriate Medication Use in Older Adults
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What are the listed side effects for diphenhydramine?
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- Hypotension
- N/V - Tachycardia - Bradycardia - Sedation - Palpitations - Drowsiness - Disturbed coordination - Dry mouth |
There is some evidence that diphenhydramine can prolong the QT-interval, leading to cardiac arrhythmias.
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What are the listed interactions for diphenhydramine?
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- Potentiated by the administration of other CNS depressants, antihistamines, narcotics, and alcohol
- MAOIs may prolong or intensify the anticholinergic effects |
As diphenhydramine slows GI transit, it can cause ulceration from local exposure when a patient is using solid forms of potassium
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What is the dosage and route of diphenhydramine?
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Adult:
- 25-50mg IVP or IM q 6-8 hours Pediatric: - 1mg/kg IVP or IO, maximum single dose is 50mg q6-8 hours |
Diphenhydramine is used recreationally as a deliriant or potentiator of alcohol.
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